A 92-year-old East County woman who gained national notoriety for selling “suicide kits” pleaded guilty in federal court Friday to a charge of failing to file a tax return.

Sharlotte Hydorn had been under investigation by federal authorities since May, when FBI agents raided her Fuerte Hills home outside of El Cajon as part of a probe into allegations of mail fraud, wire fraud, and the sale of adulterated and misbranded medical devices.

The raid came after a 29-year-old Oregon man used one of the kits to asphyxiate himself in December 2010.

In her plea Friday, Hydorn admitted to not filing a tax return in 2010. Her sentencing was set for Feb. 16, and both sides have agreed to seek a term of five years of probation for her.

In a hearing before U.S. Magistrate Judge Bernard Skomal, Hydorn answered questions in a firm and clear voice. But she declined to speak outside of court after the hearing and referred questions to her lawyer, Charles Goldberg.

Hydorn is out on $10,000 bail, and as a condition of that is not allowed to make or sell the kits. She is also prohibited under the terms of her release from advising or encouraging others to commit suicide.

The kits Hydorn sold included medical-grade tubing and a customized plastic hood that, when hooked up to a helium tank, can cause a person to pass out and die.

U.S. Attorney Laura Duffy said in a statement that the plea ends Hydorn’s “trafficking in these dangerous, unregulated devices.”

But Goldberg said the case was also brought to discourage others from following Hydorn.

“They’re trying to send a message of deterrence to discourage people from being involved in assisting in a suicide in any way,” he said.

Court documents filed in the case said that investigators found 50 San Diego County residents who had purchased the kits. The plea agreement said investigators had identified six people who had taken their lives using the materials Hydorn provided, while other court records said four deaths were connected to use of the kits.

As part of the plea agreement, the San Diego County District Attorney’s Office has agreed not to prosecute Hydorn for her involvement in those deaths. That is conditioned, however, on her not violating terms of the plea agreement and that there is not “substantial new information about her role as something other than an apparatus/information provider.”

Goldberg said that since the government raid in May, Hydorn has not sold the kits, which are promoted online and sell for $60.

Prosecutors said in court records that Hydorn sold 1,300 of the kits worldwide since 2007.

And though she pleaded to not filing a tax return for a single year, prosecutors said she had not filed a return for any years since 2007.

They also said she made more than $150,000 during that period, but Goldberg said most of her income came from a pension, Social Security and rental properties. He said it was unclear how much of her annual income came from sales of the kits.

The plea agreement said that both sides agreed the total lost in unpaid taxes is $12,500 to $30,000, but Goldberg said he plans to dispute in tax court the total tax owed and how much taxable income Hydorn had.

He also said that when investigators raided Hydorn’s home they found something curious — more than 100 uncashed checks and envelopes full of cash payments from customers who purchased the kits. He said Hydorn had never bothered to deposit the checks or cash.

“One thing that is absolutely clear is she did not do this for monetary gains,” Goldberg said. “There was never a motive to profit from this.”

Earlier this year, the Oregon Legislature banned the sale of such suicide products following the death of the man who used one of Hydorn’s kits.

She maintained she was trying to help the terminally ill make a graceful exit. Critics said she was profiting off people’s despair, noting that the Oregon man was believed to be distraught but was not incurably sick.